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♦ Intensive Selection in Your Herd
♦ Intensive Selection in Your Herd

Intensive Selection in Your Dairy Herd

Dustin Hollermann, Dairy Account Manager, Genex

The "Genomic Era" could also be called the "Age of Information." Never before has such a bombardment of genetic information been thrown onto the laps of dairy producers and their trusted advisors. It's exciting to have access to all of this information. However, it can be anything but exciting to sift through it and determine how the information can be applied to genetically improve one's dairy herd.

Intensive Selection
The genetic tools available to us consist of sire proofs, pedigree information, 3K test results, genetic ranking systems, etc. Even embryo transfer and sexed semen are genetic tools, as they influence which females or groups of females are passing their genetics on to the next generation. Things like sire summaries have been around for many years and most of the genetic progress made in dairy herds that utilize artificial insemination (A.I.) has been derived from using better service sires. Now, in this new age of information, we can use tools like genetic rankings and genomic results in conjunction with gendered semen and/or embryo transfer to add a significant amount of genetic progress from the females in a dairy herd.

Intensive selection on the female side is a new concept for the majority of commercial producers. This has traditionally been left to seedstock producers and A.I. studs to identify which females to use to create the next generation of A.I. sires. The difference is a commercial dairyman's goal is not to produce a sire for potential use in A.I., but to produce high-quality females to be used as the next generation in the milking herd. In the past, dairymen have utilized sires that meet their selection criteria and every female in the herd was bred to create a potential replacement. Now, with the use of the tools mentioned above, every dairy can select females or groups of females to use as replacement generators. On the flip-side, lower end females can be bred for purposes other than creating a female replacement or they can be used as recipient animals for embryos.

One of the first questions that must be answered when considering implementation of an intensive genetic program is how much genetic improvement can be made and does it outweigh the costs of attaining it. To answer this question, producers must determine the genetic levels of the herd's top animals and the bottom animals and the difference between them. The industry standard for determining the genetic value of an animal is Lifetime Net Merit dollars (LNM). The difference in LNM between the top animals and the bottom animals is the added value of creating a heifer from the top versus the bottom end of the herd. This is the same concept as using a better service sire to create a superior heifer versus using a lower value service sire.

In every herd, the first extra replacement generated from the herd's top animal in exchange for one less from the bottom animal is going to have the largest return on investment. As per the law of diminishing returns, once using animals from more towards the middle of the herd the return is less. This is important to keep in mind when contemplating how deep into the herd to go with intensive selection.

Determining a Herd's Top and Bottom
As stated previously, the first step in intensively selecting a female population is to benchmark their genetics. Generally, producers look to their heifers for the best genetics, although there can be high-ranking individuals in the milking string as well. One very inexpensive method to rank heifers is to simply use parent average. Most herds utilizing a DHI service would have this information available to them. If parent averages aren't available, any known pedigree information such as sire and maternal grandsire can be a starting point for ranking animals. The drawback of using only parent averages or pedigree information is the low reliability of the ranking. These methods are fairly adequate in determining if an animal is among the top half of animals in the herd; however, in order to determine the specific animals that possess the most elite genetics, higher reliabilities are desirable.

To rank animals based on a more reliable evaluation, one can turn to genomic testing. This relatively new technology can identify what genetics a particular animal likely received from her parents. The average genomic test results are very comparable to parent average LNM, but when looking for the highest or the lowest the range could be quite dramatic. Genomic test results provide a ranking at nearly twice the reliability of parent average only.

Even if genomic testing is the preferred method for ranking animals, the process still usually begins by analyzing parent averages. This is because it is often not practical (or even necessary) to test every heifer if only trying to find the top five percent or fewer to serve as flush candidates. For instance, one could rank all available animals using parent average and then genomic test only the top quarter. Even though parent averages are not as reliable, it is unlikely one of the most elite animals would get missed entirely. Using this pre-selection process will significantly keep costs down without greatly affecting the outcome.

When determining the process by which to rank animals, it is important to keep the end goal in mind; if the goal is to simply use gender-specific semen on the best half or three-quarters of the heifers and conventional on the remainder, then genomic testing might not be necessary at all. Even with less accuracy, parent averages can be a fairly good determinant of which half or even which quartile a heifer will be in. This can be easy to implement, is more practical on many commercial dairies and is still effective at ramping up genetic improvement in a herd.

In conclusion, having the ability to accurately choose which cattle your future herd will be derived from is a new and exciting practice. There are many new technologies available to enable this. Adopting these technologies to intensively select females will result in quicker genetic progress and a better herd of cows entering the milking parlor each day. Ultimately, building a better herd of cows today equates to even more superior genetics to improve upon in the generation beyond that - it's a never ending, cumulative process, but one that doesn't come without reward.


May 2011


 
 
 
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